Method of reducing and hydrogenating chemical compounds by reacting with alkali metal borohydrides



Patented July 13, 1954 OFFMIE HYDRIDES Hermann I. Schlesinger, Chicago,IlL, and Herbert C. Brown, Lafayette, Ind.

No Drawing. Application January 17, 1952, Serial No. 267,005

21 Claims.

This invention relates to methods of reducing and hydrogenating chemicalcompounds by reacting these compounds with an alkali metal borohydride.

This application is a continuation-impart of our copending applicationSerial No. 63,202, filed December 2, 1948, now abandoned, which in turwas a continuation-in-part of application Serial No. 48,314, filedSeptember 8, 1946 and now abandoned.

The alkali metal borohydrides of this invention include all of thoseboron compounds having an alkali metal associated with a groupconsisting of a boron atom and at least one and up to four reactivehydrogen atoms. When there are less than four hydrogen atoms, the groupcontaining the boron atom may contain one to three atoms other thanhydrogen or one to three radicals, which atoms or radicals arerelatively inert and non-reactive with respect to the reducing actioncharacteristic of the hydrogen atoms of these compounds, or acombination of such atoms other than hydrogen and radicals so long as atleast one hydrogen atom is present and so long as the total number ofatoms including hydrogen and radicals is four. Thus the compounds ofthis invention have the formula MBH-xAa; where :c is a whole number lessthan four and includes zero, and each A is an atom or radical, whichatom or radical is relatively inert with respect to the reducing actioncharacteristic of the hydrogen atoms of these compounds and which doesnot interfere with such reducing reaction. When is greater one, the Aradicals or atoms not all be the same. Thus the borohydrides include thecompounds MBH4, MBHzA, MBHzAz and llEHAs. The substituent A is an atomor radical as defined above. The preferred substituents are alkyl, arylor alkoxy groups, or a halide atom such as fluorine.

The general term alkali metal borohydride is used herein to include allsuch compounds While specific compounds will be identified as the simpleborohydride when a is Zero and thus four hydrogen atoms are present inthe molecule and as the substituted borohydride when at least one A ispresent so that a" is 1, 2 or 3. Thus, NaBHl the simple sodiumborohydride, NaBli CzHs s is the triethylborohydride, rasmocmn is thetrimethoxyborohydride, NaBI-HC'al-hh is the triphenylborohydride, andNaBHFz is the triiluoro borohydride. In the examples the specificboronamed are the simple borohydrides unless in naming the boroncompound a substituent is indicated.

(Cl. 260-3 l3.3)

The alkali metal borohydrides which do not contain substituents andtheir methods of preparation are described and claimed in our prior U.S. Patent 2,534,533 dated December 19, 1950. The alkali metalalkoxyborohydrides are described and claimed in our Patent 2,494,968dated January 17, 1950.

The simple sodium borohydride is a solid that is stable in dry air andreacts only very slowly with moisture in moist air. It may be heated invacuo to above 400 C. Without noticeable decomposition and is verysoluble in water. t reacts with water to liberate hydrogen, but theliberation of hydrogen is very slow if the water is at room temperatureor lower. The simple lithium borohydride reacts much more rapidly withwater and also serves to liberate hydrogen. Various methods of preparingthese simple borohydrides have been described and claimed in theabovementioned Patent 2,534,533. One of these methods is by treating analkali metal hydride with an alkyl borate. These simple borohydrides mayalso be prepared by heating an alkali metal hydride with an alkali metalalkoxyborohydride. Another method of preparation is by heating mixturesof an alkali metal and an alkyl borate with hydrogen under pressure. Afurther method of preparing these simple borohydrides is to heat analkali metal hydride with boric oxide.

We have found that both the simple and substituted lithium and sodiumborohydrides are excellent hydrogenating (reducing) agents for manytypes of organic compounds. The properties and characteristics of thecorresponding potassium compounds are, with a few minor differences,like those of the sodium compounds.

As is pointed out in the above Patent 2,494,968, the alkali metaltrialkoxyborohydrides may be prepared by reacting an alkali metalhydride with an alcohol ester of bo'ic acid at lower temperatures and indifferent proportions from those required for the simple borohydride.Similarly, other substituted borohydrides can be prepared by reactingthe alkali metal hydride M'H with the substituted boron compound BAzwhere at least one A is a substituent as defined above. Other types ofsubstituted borohydrides be prepared by disproportionation oftrisubstituted borohydrides.

Although chemical compounds which liberate hydrogen are in general goodreducing agents, there is no way of predicting the types of compoundsthat will be reduced. For example, sodium, magnesium, zinc and even tinliberate hydrogen with water or acids. of these substances reactsdifferently toward reducible compounds since the reduction potentials ofthe hydrogen liberating metals are different. As the reductionpotentials of alkali metal borohydrides were not known prior to our workwith these rfoaterials, there was no way of predicting the types ofcompounds that would be reduced with alkali metal borohydrides. Even nowthese reduction potentials of alkali metal borohydrides are not knownwith any degree of accuracy. Furthermore, the effectiveness of areducing agent depends not only on its reduction potential but also onthe rate at which reductions proceed and such rates cannot be predicted.It therefore had to be determined what kind of reductions would beproduced by the alkali metal borohydrides. The liberation of hydrogen isnot an essential part of the reducing action. This is shown by the factthat the compounds of this invention react as reducing agents insolvents such as the primary amines, but they do not liberate hydrogentherefrom. Furthermore, sodium borohydride liberates hydrogen from watervery slow ly and the reaction becomes exceedingly slow after a fewminutes when the solution has become moderately alkaline. Neverthelessthe reducing is usually quite rapid and complete. No other readilyavailable hydrides that are active as reducing agents can be used in allthe solvents and carriers in which the alkali metal borohydrides areeffective.

The alkali metal bcrohydrides are particularly useful as they may beemployed as reducing agents in a variety of solvents. Thus, certain ofthe borohydrides may be employed in aqueous solutions, in solution inother solvents, suspended in a liquid carrier, or dissolved or suspendedin the chemical compound that is to be reduced. Typical solvents otherthan water include: liquid ammonia; primary and secondary amines such asmethyl amine, ethyl amine, isopropyl amine, diethylamine, ethylenediamine, pyridine and derivatives of such amines containing etherlinkages; and alcohols, particularly aliphatic alcohols such as methyl,ethyl and isopropyl alcohol, as well as alcohols containing ether oramine linkages or both. Certain of the alkali metal borohydrides mayalso be employed in suspension in an ether or other carrier. Lithiumborohydride may be used in these solvents as well as in many ethers inwhich sodium borohydride d es not dissolve. If aqueous solutions are tobe used, the sodium borohydride is preferred since the initial reactionof lithium borohydride with water is very vigorous even though it soonsubsides. The vigor of this initial reaction may be de-- creased byemploying alkaline solutions rather than pure water as a solvent. Iflithium borohydride is used in aqueous solution, it is preferable toexclude air during its addition to aqueous solutions or to water. 011the other hand. lithium borohydride is preferred where compounds solublein ethers, but not soluble in water, are to be reduced or when thepresence of water or basic substances cause undesirable side reactions.

In general, the solvents and carriers that may be used cover a widerange. As has been pointed out, even those liquids such as ethers inwhich the particular alkali metal borohydride such as sodiumalkoxyborohydride is not soluble may be used by merely suspending theborohydride in the liquid. The reductions may be accomplished withoutthe use of an added solvent or carrier when the chemical compounds thatare reduced are themselves liquid at the reaction temperature. Here thealkali metal borohydride is merely mixed with the liquid chemicalcompound and no added solvent or other medium is necessary. Theversatility of the alkali metal bcrohydrides with respect to the varietyof solvents in which they may be selectively used and with respect tothe great variety of substances which they reduce rapidly at low ormoderate temperatures with good yields are among the chief advantages oftheir use.

The alkali metal borohydrides described herein are useful in reducing orhydrogenating a chemical compound containing a reducible functionalgroup including an atom other than hydrogen and carbon. They areparticularly effective for selective hydrogenations or reductions. Thus,1-5 is possible to hydrogenate an aldehyde, ketone, acid chloride, acidanhydride, or ester group in the presence of double or triple bondswithout simultaneously hydrogenating the double or triple bond. Evenmore remarkable is the fact that these reagents permit the hydrogenationof an aldehyde or ketonc group in a molecule without simultaneouslyhydrogenating another functional group such as an ester, amide, nitrileor nitro groups which may also be present in the same molecule.Moreover, an acid chloride group for example, is readily hydrogenatedand can be hydrogenated to either the aldehyde stage or the alcoholstage without simultaneously hydrogenating at other points such as atdouble bonds or ester, amide, nitrile or nitro groups. As can be seentherefore, these new reagents permit hydrogenation of selected groups inlarge organic molecules containing more than one functional group. Theytherefore facilitate the synthesis of large poly-functional moleculessuch as are of importance in the pharmaceutical field as well as in thefield of natural products.

The reductions by means of the alkali metal borohydrides according tothis invention sometimes lead to the formation of intermediate productswhich are then hydrolyzed to obtain the desired. end product. Even whenwater is present as a solvent or carrier, it is sometimes necessary toraise the temperature in order to accomplish this result. Water is alsosometimes added at the end of the reaction in order to remove excessborohydride.

The following examples are used for illustration purposes only to showthe remarkable versatility and selectivity of the borohydrides inhydrogenating organic compounds.

The hydrogenation of butyraldehyde Sodium borohydride, 38 g. (1.00 mole)is dissolved in 500 ml. cold water and placed in a 2- literround-bottomed flask fitted with a stirrer, a condenser, and a droppingfunnel. In the dropping funnel is placed 328 g. of freshly distilledn-butyraldehyde (4.00 mole) and the alde hyde is added slowly over aperiod of four hours to the flask maintained at 25 C. After all of thealdehyde is added, the reaction mixture is stirred for an additional twohours. The upper organic layer is separated from the lower aqueouslayer, washed with several small portions of water, and distilled. Thereis obtained 2'70 g. of n-butyl alcohol, B. P. -118, 12. 1.3977.

The hydrogenation of benzaldehyde In a 1-liter round-bottomed flaskfitted with a condenser and stirrer is placed 53 g. (0.50 mole) offreshly distilled benzaldehyde dissolved in 200 g. methanol. To thereaction mixture is added 9.5 g. (0.25 mole) of sodium borohydride insmall quantities over a period of one hour, the mixture is permitted tostand for two additional hours until hydrogen evolution has ceased. Thereaction mixture is then poured into 500 ml. of water, stirredthoroughly, and the upper organic layer is separated. The lower aqueouslayer is extracted with several portions of ether and the either extractis added to the organic layer previously separated. The combined organicmaterial is dried over calcium hydride and then distilled through aVigreaux column. The benzyl alcohol is collected at 95 at 11 mm., n1.5375. The yield is 48 g., 90% of the calculated.

The hydrogenation of cinnamaldehyde In a B-neck l-liter round-bottomedflask fitted with a stirrer, condenser and dropping funnel, is

placed g. of sodium trimethoxyborohydride rate as to maintain the etherat a gentle reflux. L

After all of the aldehyde is added, the flask is gently heated for twoadditional hours. The reaction mixture is allowed to cool to roomtemperature and 200 ml. of water is added carefully. The reactionmixture is poured into 1- liter separatory funnel and the upper etherlayer is separated and dried over sodium sulfate. The ether is removedby distillation over a steam cone and. the product is distilled undervacuum in a distilling flask equipped with a short Vigreaux column. Theproduct cinnamyl alcohol is collected at 133-137 at 13 mm., n 1.5825.The yield is 57 g., 85% or" theoretical. The value of the refractiveindex indicates the absence of any but possible traces of hydrocinnarnylalcohol.

The same reduction can be carried out with lithium borohydride dissolvedin ether, potassium borohydride and sodium triethoxyborohydride eitherdissolved in ethanol or suspended in ethyl ether.

The hydrogenation of chloral In a 1-liter, round-bottomed flask isplaced 2.2 g. (0.10 mole) of lithium. borohydride and 200 m1. ofanhydrous ether. In the dropping funnel is placed 53 g. (0.40 mole)chloral dissolved in 100 ml. ethyl ether. The chloral solution is addedslowly to the reaction mixture. There is a vigorous reaction and theether refiuxes. The addition is maintained at such a rate as to maintainthe ether at a gentle reflux. After all of the chloral has been added,the reaction mixture is heated under reflux for an additional two hoursand 300 ml. of water is then added. The ether layer is separated. Theaqueous layer is extracted with several additional. portion of ether.The combined ether extracts are dried over sodium sulfate and the etherremoved by distillation over a steam cone. The product is then recoveredby distillation from a Claisen flask in vacuum. 8-, 5-,{i-Trichloroethanol, B. P. 147-151, M. P. 16-17", is obtained in 70%yield, 41 g.

The hydrogenation of beneoyl chloride In a 1-liter round-bottomed flaskis placed 100 ml. of purified dioxane and 7 .6 g. (0.20 mole) of sodiumborohydride. The reaction mixture is cooled. and to the suspension isadded a solution of benzoyl chloride, 28 g. (0.20 mole) in 100 ml. ofthe solvent. After addition is complete, the reaction mixture isrefluxed gently for two hours. The reaction mixture is cooled and wateradded to decompose the excess sodium boro hydride. This mixture of waterand dioxane is distilled off at atmospheric pressure. Water is added tothe residue to dissolve the salts, the organic material is taken up inether. Distillation of the ether extract yields g. benzyl alcohol, 70%yield, n 1.5373, B. P. 93-96 at 11 mm.

The hydrogenation of heneoyl chloride In a l-liter round-bottomed flaskfitted with a condenser, stirrer and dropping funnel is placed 200 ml.of anhydrous ethyl ether and 128 g. (1.00 mole) of sodiumtrimethoxyborohydride. To the stirred suspension is added a solution of70 g. benzoyl chloride (0.50 mole) dissolved in anhydrous ethyl ether. Avigorous reaction ensues. The acid chloride should be added to thehydrogenation agent slowly, at such a rate that the ether reiiuxesgently. fter the acid chloride has been added, the mixture is permittedto stand for 1 hour and 200 ml. of water is added. The reaction mixtureis then poured into a separatory funnel, the ether layer is separatedand dried with calcium hydride. The ether is removed on a steam cone andthe benzyl alcohol is obtained by distillation under vacuum. The productyield is 19 g., B. P. 93-96" at 11 mm, 12 1.5375. -he yield is 90% ofthe theoretical.

13y addition of sodium trimethoxy'oorohydride (1.00 mole) to henzoylchloride (1.00 mole) in ether at 0, benzaldehyde is formed. Thebenzaldehyde is conveniently recovered as its hisulfite additioncompound. It was converted into the phenylhydrazone, M. P. Ida-156.

The hydrogenation of n-hutyric anhydricie in a 1-liter round-bottomedflask is placed 19 sodium horohydride (0.50 mole) or 128 g. sodiumtrimethoxyborohydride (1.0 mole) and 100 ml. of n-butyl ether. To thereaction mixture is added 79 g. or" n-hutyric anhydride in 100 ml. ofn-butyl ether. The mixture is heated under reflux for 4 hours. Thereaction mixture is allowed to cool, and 200 m1. of a dilute aqueoussolution of sulfuric acid is added to decompose excess borohydride. Whenhydrogen is no longer given off, the n-butyl ether layer is separated.The ether layer is treated with 200 ml. of a 6M solution of sodiumhydroxide. The aqueous extract is acidified with sulfuric acid. Theupper layer is taken up in ether. dried with calcium sulfate anddistilled at atmospheric pressure. There is obtained 26 g. of n-butyricacid, B. P. Nil-163, 11 1.3980. The yield is 60% of the0- retioal. The nbutyl ether layer (from which the acid has been extracted) is dried withcalcium sulfate and distilled through a 30 cm. column, packed with 3/36stainless steel helices. There is obtained 20 g. n-butyl alcohol, B. P.114-117", n 1.3980. The yield is of theo retical. Only one of the twocarbonyl groups in the anhydride undergoes reduction. In the case ofcyclic anhydrides, such as phthalic anhydride or succinic anhydride, thehydrogenation affects only one of the two carbonyl groups in a similarmanner and results in the formation of butyrolactone, B. P. 197-200 andphthalide, M. P. -72", in yields of 40-60%,

The hydrogenation of ethyl beneoate In a 1-liter round-bottomed flask,fitted with stirrer, condenser and dropping funnel, is placed 4.4 g. oflithium borohydride (0.2 mole) in ml. tetrahydrofuran and the reactionmixture is The hydrogenation of ethyl benzoate The ethyl benzoate, 30 g.(0.2 mole) is added to the sodium trimethoxyborohydride, 32 g. (0.25mole) suspended in 200 ml. n-butyl ether. The reaction mixture isrefluxed for 10 hours. At the end of this time, water is added and theether layer is separated and distilled through an efficient column.There is obtained 9.5 g. (B. P. 93-96 at 11 mm., 11 1.5373) of benzylalcohol, a yield of 45%.

The hydrogenation of p-nitrobenzaldehyde The remarkable selectivity ofthe reagent is illustrated by the hydrogenation of p-nitrobenzaldehyde.

The p-nitrobenzaldehyde is dissolved in methanol and the sodiumborohydride is added in small quantities in the molar ratiolNaBHap-NOzCal-RCHO. The reaction mixture is maintained between and forfour hours. Water is then added and the organic layer is separated andcrystallized from ligroin. From g. of the aldehyde (0.10 mole) there isobtained 12 g. of p-nitrobenzyl alcohol, M. P. 93, a yield of 80%. Noreduction of the nitro group occurs under these conditions.

The hydrogenation of p-cyanoaceiophenone The hydrogenation ofp-cyanoacetophenone may be carried out by a procedure identical withthat described above. The product is recrystallized from ligroin. From14.6 g. of the ketone there is obtained 10 g. ofp-cyanophenylmethflcarbinol, B. P. 140-144" at 6 mm., n 1.5480 a yieldof 65%. No reduction of the cyano group occurs under these conditions.

The hydrogenation of acetone Solid sodium borohydride was added toacetone in the presence of water. The reaction was quite rapid and thefinal product was predominantly isopropyl alcohol with some pinacolsbeing formed. The formation of pinacols indicated that a certain degreeof condensation occurred.

The hydrogenation of methyl ethyl Icetone A solution of 3 to 4 grams oflithium borohydride in 95 grams of diethyl ether was placed in a 500 cc.three-necked flask equipped with reflux condenser, dropping funnel, andmechanical stirrer, and protected from moisture unti1 completion of thereaction by calcium chloride tubes attached to the openings. Through thedropping funnel, 33.2 grams of methyl ethyl ketone was introduced at arate such as to produce gentle reflux. One hour after the last of theketone had been added and with continued stirring, cc. of a 15%hydrochloric acid solution was slowly added. The aqueous layer wassaturated with sodium chloride. After separation of the ether layer, theaqueous layer was washed twice with ether. The product obtained afterevaporation of the ether from the dried ether layer was fractionallydistilled in a Vigreaux column, whereupon 33.7 grams (a 92% yield) ofbutano1-2 (B. P. 98.5) (749 mm.)) was secured.

The hydrogenation of methyl Zaumte A solution of 3 to 4 grams of lithiumborohydride in 72 grams of diethyl ether was placed in the apparatusdescribed in the preceding paragraph and 31.7 grams of methyl lauratewas added. There was no immediate reaction, but after stirrin for a fewminutes, sufficient heat was evolved to cause the solution to boil. Themixture was refluxed (heating with a Glas-Col) with continuous stirringfor six hours. After cooling with an ice bath, 100 cc. of 10% sulfuricacid was slowly added. The other layer was separated, dried, and theether evaporated 01f. Last traces of moisture were removed from theproduct by heating at 80 C. and 15 mm. pressure. Lauryl alcohol wasobtained with a M. P. of 22.523 and in a yield of 97%.

The hydrogenation of cinnamaldehyde In a small tube connected to a highvacuum apparatus is placed 2.3 g. of sodium hydride (0.1 mole) and 14.7g. (0.15 mole) of triethylboron is added in several small portions, eachportion being added only after the previous material had reacted. Whenno further reaction is observed, the volatile material is removed-itconsists of 4.9 g. of triethylboron. To the product in the tube, sodiumtriethylborohydride, is added 20 ml. of ether and 13. 2 g. (0.1 mole)cinnamaldehyde. A vigorous reaction ensues. Nitrogen is introdduced intothe tube and it is removed from the vacuum apparatus, and then water anddilute acid are added to hydrolyze the product. The upper layer isseparated, dried with anhydrous magnesium sulfate, and distilled in asmall Claisen flask in a nitrogen atmosphere. After the fractions ofether and triethylboron are removed, the product, cinnamyl alcohol, 11.1.5825, is collected at -140" at 13 mm.

Other and similar reductions and hydrogenations with alkali metalborohydrides have been described in the literature. of the AmericanChemical Society, vol. 71 at pages 122 and 324.7 discuss reductions withalkali metal borohydrides including the following: nheptaldehyde ton-heptanol, benzaldehyde to benzyl alcohol, crotonaldehyde to crotylalcohol, methyl ethyl ketone to s-butanol, benzophenone to benzhydrol,n-butyl palmitate to n-hexadecanol, ethyl benzoate to benzyl alcohol,ethyl sebacate to decamethylene glycol, beta-benzoylpropionic acid togamma-phenylbutyrolactone, ethyl levulinate to gamma-valerolactone,m-nitroacetophenone to a-(m-nitrophenyl)-ethanol, acetonyl-acetone tohexanediol-2, 5, n-butyraldehyde to n-butanol, chloral hydrate to2.2.2-trichloroethanol, cyclopentanone to cyclopentanol, diacetyl tobutanediol-Z, 3, levulinic acid to gam- Thus, theJournalma-valerolactone, mesityl oxide to 4-methyl-3- pentenol-Z,anisaldehyde to anisyl alcohol, benzil to hydrobenzoin,bromoacetophenone to styrene bromohydrin, cinnamaldehyde to cinnamylalcohol, dicyclohexyl ketone to dicyclohexylcarbinol,pdimethylaminobenzaldehyde to p-dimethylaminobenzyl alcohol,m-hydroxybenzaldew hyde to m-hydroxylbenzyl alcohol,rn-nitrobenzaldehyde to m-nitrobenzyl alcohol, benzoyl chloride tobenzyl alcohol, n-butyry1 chloride to nbutanol, cinnamoyl chloride tohydrocinnamyl alcohol, monoethyl succinate acid chloride tobutyrolacetone, palmitoyl chloride to cetyl alcohol, and o-phthaly],chloride to phthalide.

The alkali metal borohydrides like aluminum containing hydridesdescribed and claimed in H. I. Schlesinger and A. E. Finholt applicationSerial No. 752,286, filed June 3, 1947, which issued as Patent No.2,576,311 on November 27, 195i, effective in solution, react rapidly,produce good yields, avoid side reactions in the case of many organicsubstances and are effective at room ten pera-tures at which many otheragents do not react. Although the borohydrides are much like thecorresponding aluminum compounds as reducing agents there are importantdifferences. Thus, the borohydrides may be used in water or in alcoholsin which the aluminum compounds react violently and may also be usedwith amines and with liquid ammonia. The borohydrides are generally morestable than the aluminohydrides and can be used over a wider range oftemperatures. For example, sodium borohydride is stable thermally at 4000., whereas lithium aluminum hydride decomposes rapidly at temperaturesof about 175-200" C.

The terms hydrogenation and reduction are used interchangeably herein.

Having described our invention together with certain embodimentsthereof, it is our intention that the invention be not limited by any ofthe details of description unless otherwise specified, but rather beconstrued broadly within its spirit out in the accompanying claims.

We claim:

1. In the redu containing a ing an other hich comprises metalhorohydride at a tement to cause a chemical reaction y low thatborohydride does ide tr e formula .TA.3: wherein M is an alkali metal,:8 is a is number less t an four including zero, and a is member of theclas consisting of an inert and relatively non-reactiv atom and radical.

2. The method of claim 1 wherein the alkali metal of the borohydride issodium.

3. The method of claim 1 wherein the alkali metal of the borohydride islithium.

4. The method of claim 1 wherein the alkali metal of the borohydride ispotassium.

5. The method of claim 1 wherein the chemical compound contains acarbonyl functional group.

6. In the reduction of a chemical compound containing a reduciblefunctional group including an atom other than hydrogen and carbon, thestep which comprises associating the compound with an alkali metalborohydride in a liquid carrier and. at a temperature sufficient tocause a chemical reaction but sumciently low that said borohydride doesnot substantially 1o thermally decompose during the reduction, saidborohydride having the formula MBHi-aAx wherein M is an alkali metal, a:is a whole number less than four including zero, and A is a member ofthe class consisting of an inert and relatively nonreactive atom andradical.

7. The method of claim 6 wherein the alkali metal of the borohydride issodium and the carrier is an ether in which the alkali metal borohydrideis suspended.

8. The method of claim 6 wherein the alkali metal of the borohydride issodium and the carrier is polar solvent for the alkali metalborohydride.

9. The method of claim 6' wherein the carrier is water in which theborohydride is at least par ially soluble.

10. The method of claim 6 wherein the alkali metal oi the borohydride islithium and the carrier is an ether in the alkali metal borohy ride isdissolved.

11. The method of claim 6 wherein the carrier is an amine in which theborohydride is at least partially soluble.

12. The method of claim 6 wherein the carrier is an alcohol in which theborohydricle is at least partially soluble.

13. In the reduction of a hydrocarbon derivative compound containing acarbonyl functional group, the step which comprises associating saidcompound with an alkali metal borohydride at a temperature sufficient tocause a chemical reaction but sufficiently low that borohydride does notsubstantially thermally decompose during the reduction and in thepresence of a carrier for the borohydride, said borohydride having theformula MEI-lama wherein M is an alkali metal, .r is a whole number lessthan four including zero, and A is a member of the class consisting ofan inert and relatively non-reactive atom and radical.

14. In the reduction of a hydrocarbon derivative compound containing analdehyde functional group, the step which comprises associating saidcompound with an alkali metal borohyclride at a temperature sufficientto cause a chemical reaction but sufiiciently low that said borohydridedoes not substantially thermally decompose during the reduction and inthe presence of a carrier for the borohydride, said borohydride havingthe formula MBH-IAr wherein M is an alkali metal, as is a whole numberless than four including zero, and A is a member of the class consistingof an inert and relatively non-reactive atom and radical.

15. In the reduction of a hydrocarbon derivative compound containing aketone functional group, the step which comprises associating saidcompound with an alkali metal borohydride at a temperature sufficient tocause a chemical reaction but sufficiently low that said borohydridedoes not substantially thermally decompose during the reduction and inthe presence of a carrier for the borohydride, said borohydride havingthe formula IViBH4:cA. r wherein M is an alkali metal, a: is a wholenumber less than four including zero, and A is a member of the classconsisting of an inert and relatively non-reactive atom and radical.

16. In the reduction of a hydrocarbon derivative compound containing anester functional group, the step which comprises associating saidcompound with an alkali metal borohydride at a temperature sufiicient tocause a chemical reaction but suiiiciently low that said borchydridedoes not substantially thermally decompose during the reduction and inthe presence of a carrier for the borohydride, said borohydride havingthe formula MBH-azAa: wherein M is an alkali metal, a: is a whole numberless than four including zero, and A is a member of the class consistingof an inert and relatively non-reactive atom and radical.

1'7. In the reduction of a hydrocarbon derivative compound containing anacid anhydride functional group, the step which comprises associatingsaid compound with an alkali metal borohydride at a temperaturesuficient to cause a chemical reaction but sufficiently low that saidborohydride does not substantially thermally decompose during thereduction and in the presence of a carrier for the borohydride, saidborohydride having the formula MBHi-xAx wherein M is an alkali metal,:1: is a whole number less than four including zero, and A is a memberof the class consisting of an inert and relatively non-reactive atom andradical.

18. In the reduction of a hydrocarbon derivative compound containing anacid halide functional group, the step which comprises associating saidcompound with an alkali metal borohydride at a temperature sufiicient tocause a chemical reaction but sufiiciently low that said borohydridedoes not substantially thermally decompose during the reduction and inthe presence of a carrier for the borohydride, said borohydride havingthe formula MEI-Lame wherein M is an alkali metal, m is a whole numberless than four including zero, and A is a member of the class consistingof an inert and relatively non-reactive atom and radical.

19. In the reduction of a chemical compound containing a reduciblefunctional group including an atom other than hydrogen and carbon, saidcompound being reducible in an aqueous solution, the step whichcomprises associating the compound with an alkali metal borohydride inan alkaline medium at a temperature sufiicient to cause a chemicalreaction but suificiently low that said borohydride does notsubstantially i2 thermally decompose during the reduction, saidborohydride having the formula MEI-Lam; wherein M is an alkali metal, a:is a whole number less than four including zero, and A is a member ofthe class consisting of an inert and relatively non-reactive atom andradical.

20. In the reduction of a chemical compound containing a reduciblefunctional group including an atom other than hydrogen and carbon, thestep which comprises associating the compound with an alkali metalborohydride in a nonaqueous medium at a temperature sufficient to causea chemical reaction but sufficiently low that said borohydride does notsubstantially decompose during the reduction, and then hydrolyzing theresulting product, said borohydride having the formula MBIIi-IAI whereinM is an alkali metal, a: is a whole number less than four includingzero, and A is a member of the class consisting of an inert andrelatively non-reactive atom and radical.

21. In the reduction of a chemical compound containing a reduciblefunctional group including an atom other than hydrogen and carbon, thestep which comprises associating the compound with an alkali metalborohydride at a temperature sufiicient to cause a chemical reaction butsufficiently low that said borohydride does not substantially decomposeduring the reduction, said compound being liquid at the reactiontemperature and serving as a carrier for the borohydride, saidborohydride having the formula l\/IBI'I4-:Aa: wherein M is an alkalimetal, a: is a whole number less than four including zero, and A is amember of the class consisting of an inert and relatively non-reactiveatom and radical.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,534,533 Schlesinger et al. Dec. 19, 1950 2,576,311Schlesinger et al. Nov. 27, 1951

1. IN THE REDUCTION OF A CHEMICAL COMPOUND CONTAINING A REDUCIBLEFUNCTIONAL GROUP INCLUDING AN ATOM OTHER THAN HYDROGEN AND CARBON, THESTEP WHICH COMPRISES ASSOCIATING THE COMPOUND WITH AN ALKALI METALBOROHYDRIDE AT A TEMPERATURE SUFFICIENT TO CAUSE A CHEMICAL REACTION BUTSUFFICIENTLY LOW THAT SAID BOROHYDRIDE DOES NOT SUBSTANTIALLY THERMALLYDECOMPOSE DURING THE REDUCTION, SAID BOROHYDRIDE HAVING THE FORMULAMBH4-XAX WHEREIN M IS AN ALKALI METAL, X IS A WHOLE NUMBER LESS THANFOUR INCLUDING ZERO, AND A IS A MEMBER OF THE CLASS CONSISTING OF ANINERT AND RELATIVELY NON-REACTIVE ATOM AND RADICAL.